Fortheages on "[Theme: Decode] Changing Page Title Font"

Hi,
I’m pretty much a beginner in WordPress and I’ve just started a Web site. How would I go about changing the font size of a page title in the theme? The following URL will take you to the site and “About Us” under the header is what I’m referring to: http://www.dunamismedical.com/about-us/. I have installed the plug-in My Custom CSS in case that can simplify a solution.
Thanks and regards,
Lee